MK Sound LFE-4 operation manual Grounding, General Connection Guidelines

Bass Management Controller

Input and Output Connector Wiring

The XLR connectors on the LFE-4 are wired as follows:

Pin 3:	Minus
Pin 2:	Plus
Pin 1:	Ground

General Connection Guidelines

To avoid loud transients that may damage your speakers and hurt your ears, turn off your power amplifiers before connecting or disconnecting any cables or the power supply on the LFE-4.

Certain types of audio cables have high capacitance in the range of 0.75pf/ft. Long runs of high capacitance cable can cause a decrease in high frequency performance of the LFE-4. Approximately 300 feet of 0.75pf/ft cable will cause a drop of 3dB at 24kHz. In order to keep this effect to a minimum, use high-quality, low capacitance cable or keep your cable runs from the LFE-4 to your amplifier to under a hundred and fifty feet.

5.GROUNDING

The LFE-4 was designed so as not to add noise to an already clean system. To eliminate the possibility of the extra safety ground introducing ground loop hum, the LFE-4 uses an external double-insulated UL approved power transformer that does not require a safety ground. The LFE-4 is grounded to the audio signal ground of the mixer and power amplifiers through the XLR cables. In order to minimize the grounding problems between the LFE-4 and equipment racks, the internal audio signal ground can be separated from the chassis ground. On the rear of the unit are two binding posts. The black binding post is connected to the chassis. The red binding post is connected to the audio signal ground. Normally, these binding posts are shorted together with a gold-plated jumper. However in a situation where the chassis may be connected to a "dirty" ground, this jumper can be removed, separating the audio and chassis ground. In addition, the binding post can be used to attach an additional heavy gauge grounding wire.

FIGURE 3:	GROUNDING	Ground to clean
		audio ground	Remove jumper
		if necessary

SIGNAL	CHASSIS
GND	GND
	Ground to
24 VAC	rack
IN

TECHNICAL TIP:

It is sometimes a common practice to only ground XLR cables at one end to prevent ground loops through the cable. In order to work correctly, the LFE-4 must be grounded to either the mixing console or the power amps or both. This is normally done through the XLR cables. If you are using XLR cables with the shield disconnected at one end for both inputs and outputs, you must use the RED binding post to connect the LFE-4 to the audio system ground.

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